The DNA repair studies reported here are being expanded into 2 areas. Attempts are being made to measure (1) DNA repair synthesis in Mouse Epidermal Cells in tissue culture, and to determine the effects of tumor-promoting agents (primarily TPA and anthralin) on DNA repair synthesis in these cells. (2) Other studies are being carried out to compare the characteristics of DNA repair synthesis induced by NA-AAF and by ECU (ethoxy-carbonyl-urethan) in WI-38 cells.